The present invention relates to a liquid level detecting apparatus, and particularly has a feature in miniaturization of a liquid level detecting apparatus.
A conventional liquid level detecting apparatus 71 is disclosed in Japanese Utility Model Laid-Open No. 2029/1993, and as shown in FIG. 13 and FIG. 14, a float arm 72 having a tip end at which a not shown float moving according to variation of a liquid level is provided, is rotatably supported in a main body frame 73. The float arm 72 is rotatably supported in the main body frame 73 through an arm holder 74.
A contact holding member 75 is fixed to the arm holder 74, and a sliding contact 76 is protrusively provided at the tip end of the contact holding member 75. A pair of holding pieces 74a are formed at the arm holder 74 in order to position the float arm 72 and the contact holding member 75 held by the arm holder 74, the opposing surfaces of the holding pieces 74a are formed into arc surfaces to conform to the outer shape of the float arm 72, the float arm 72 is press inserted into the arc surfaces from an upper opening portion of the holding pieces 74a while spreading the holding pieces 74a, and a structure is realized in which the float arm 72 does not come out toward the upper portion by elastic restoring force of the holding pieces 74a. 
The sliding contact 76 slides on a circuit board 77 provided in the main body frame 73 and made of ceramic at a predetermined contact pressure.
The circuit board 77 is provided, on its surface, with a not-shown band-like resistor and a not-shown comb electrode arranged into a band along the band-like resistor, the sliding contact 76 is made to slide on and come in contact with the comb electrode at the predetermined contact pressure, and a current variation corresponding to the quantity of varying resistance between the sliding contact 76 and the base end of the resistor is outputted, so that the liquid quantity is detected.
In the liquid level detecting apparatus 71 like this, a bearing structure of the float arm 72 is such that a bearing fit portion 78 is formed in the main body frame 73, a two-stage cylindrical bearing member 79 having different diameters is rotatably fitted in the bearing fit portion 78, an end portion 82 of the float arm 72 bent into an L shape in a substantially rectangular direction is inserted to pass through a shaft hole 80 provided in the bearing member 79 and a shaft hole 81 provided in the base portion of the arm holder 74, a push nut as a falling out preventing member 83 is press fitted to a through end portion 82a of the end portion 82 protruding from the lower surface of the bearing member 79, and the float arm 72 is pulled downwardly from the bearing member 79 by the press fitting of the push nut 83 and is clamped.
A receiving surface 85 for receiving a flange engagement portion 84 formed by header working at the outer periphery of the middle of the end portion 82 of the float arm 72 is formed at a hole fringe portion of the shaft hole 81 of the arm holder 74, and a contact surface 86 is formed at a position where the main body frame 73 is in contact with the bearing member 79. The arm holder 74 receives the engagement portion 84 of the float arm 72 at the receiving surface 85, and the float arm 72, the arm holder 74, and the contact holding member 75 are fitted to one another so that they do not rattle. Accordingly, when the push nut 83 is fastened, the bearing member 79 is fixed in a state where it is fastened by both the arm holder 74 and the push nut 83, and a structure is realized in which the float arm 72 and the bearing member 79 are rotated together. An upward force is always applied to the arm holder 74 by a coil spring 87 electrically connected to the contact holding member 75. A stepped portion 78a of the bearing fit portion 78 and a stepped portion 79a of the bearing member 79 receive the upward force of the coil spring 87, and the float arm 72, together with the bearing member 79, does not come out toward the upside. Since the bearing member 79 protrudes from the main body frame 73 to come in contact with the arm holder 74, and the main body frame 73 is separate from the arm holder 74, the combination of the float arm 72, the arm holder 74 and the bearing member 79 is rotated relative to the main body frame 73.
Incidentally, reference numerals 88 and 89 designate terminals, the one terminal 88 is connected to the circuit board 77, and the other terminal 89 is connected to the contact holding member 75 through the coil spring 87.
In recent years, the liquid level detecting apparatus 71 installed in a not-shown fuel tank, a fuel pump and the like are installed as a combined unit in the fuel tank. From a problem of fitting caused from the formation of the unit and so on, the liquid level detecting apparatus 71 is also desired to be miniaturized. Then, an object is to provide a liquid level detecting apparatus which can achieve miniaturization.
A liquid level detecting apparatus of the present invention comprises a float arm provided with a float floating on a liquid surface, an arm holder for holding the float arm and provided with shaft portions as rotation supporting points of the float arm, a main body frame provided with two bearing portions for axially supporting the shaft portions of the arm holder, a circuit board fixed to the main body frame, and a contact holding member provided with a sliding contact sliding on the circuit board and fixed to the arm holder, and the arm holder is positioned between the bearing portions and holds the float arm and the contact holding member. By the structure like this, the liquid level detecting apparatus capable of achieving miniaturization can be provided. Besides, the shaft portions are supported by the two portions of the bearing portions, so that it is possible to provided the liquid level detecting apparatus which is small and in which the axes of the shaft portions are hard to shift.
Besides, a liquid level detecting apparatus comprises a float arm provided with a float floating on a liquid surface, an arm holder for holding the float arm and provided with shaft portions as rotation supporting points of the float arm, a main body frame for axially supporting the shaft portions of the arm holder, a circuit board fixed to the main body frame, and a contact holding member provided with a sliding contact sliding on the circuit board and fixed to the arm holder, in which the two separate shaft portions are provided at the arm holder, two bearing portions for axially supporting the two shaft portions are provided at the main body frame, and the arm holder holding the front arm and the contact holding member is provided between the bearing portions. By the structure like this, the liquid level detecting apparatus,capable of achieving miniaturization can be provided. Besides, the shaft portions are supported at two places of the bearing portions, so that it is possible to provided the liquid level detecting apparatus which is small and the axes of the shaft portions are hard to shift.
Besides, a liquid level detecting apparatus comprises a float arm provided with a float floating on a liquid surface, an arm holder for holding the float arm and provided with shaft portions as rotation supporting points of the float arm, a first frame constituting a main body frame and provided with a first bearing portion for axially supporting the shaft portion of the arm holder, a second frame constituting the main body frame and provided with a second bearing portion for axially supporting the shaft portion of the arm holder, a circuit board fixed to the first frame, and a contact holding member including a sliding contact sliding on the circuit board and fixed to the arm holder, the arm holder is held by the first and the second frames, and the first and the second frames are fixed. By the structure like this, as compared with the prior art, a holding method of the arm holder is changed, and the number of parts is reduced, so that the liquid level detecting apparatus capable of achieving miniaturization can be provided. Besides, the shaft portions are supported at the two places of the first and the second bearing portions, so that it is possible to provide the liquid level detecting apparatus which is small and in which the axes of the shaft portions are hard to shift.
Besides, a liquid level detecting apparatus comprises a float arm provided with a float floating on a liquid surface, an arm holder for holding the float arm and provided with shaft portions as rotation supporting points of the float arm, a main body frame for axially supporting the shaft portions of the arm holder, a circuit board fixed to the main body frame, and a contact holding member provided with a sliding contact sliding on the circuit board and fixed to the arm holder, in which the two separate shaft portions are provided at the arm holder, the main body frame is formed of a first frame and a second frame, the circuit board is fixed to the first frame which is provided with a first bearing portion for axially supporting the shaft portion of the arm holder, the second frame is provided with a second bearing portion for axially supporting the shaft portion of the arm holder, the arm holder is held by the first and the second frames, and the first and the second frames are fixed. By the structure like this, as compared with the prior art, a holding method of the arm holder is changed, and the number of parts is reduced, so that the liquid level detecting apparatus capable of achieving miniaturization can be provided. Besides, the shaft portions are supported at the two places of the first and the second bearing portions, so that it is possible to provide the liquid level detecting apparatus which is small and in which the axes of the shaft portions are hard to shift.
Besides, the first and the second frames are fixed by welding. By the structure like this, it is possible to provide the liquid level detecting apparatus in which the first and the second frames can be fitted to each other more firmly.
Besides, a holding arm piece formed to extend in a direction vertical to the axial direction is formed between the shaft portions of the arm holder, and the float arm and the contact holding member are held by the holding arm piece. By the structure like this, it is possible to provide the liquid level detecting apparatus in which the float arm and the contact holding member can be easily fixed and the fitting work is excellent.
Besides, a bent portion is provided at which an end portion of the float arm is bent in a direction intersecting with the shaft portions, and the arm holder is provided with a holding portion for rotatably holding the end portion and a holding piece for preventing rotation of the float arm. By the structure like this, it is possible to provide the liquid level detecting apparatus in which fitting of the float arm to the arm holder can be easily made.
Besides, a bending direction of the end portion is substantially orthogonal to the axial direction of the shaft portions. By the structure like this, the distance between the bearing portions can be made short, and the smaller liquid level detecting apparatus can be provided.
Besides, the main body frame is provided with a guide portion for suppressing movement of the float arm in a rotation axis direction. By the structure like this, it is possible to provide the liquid level detecting apparatus in which the movement of the arm holder in the rotation axis direction can be suppressed, the float arm can be easily fitted to the arm holder, and it does not easily come off.
Besides, a concave-convex fit portion is provided near the first and the second bearing portions of the first and the second frames. By the structure like this, a construction is obtained in which the axial centers of the bearing portions are hard to shift, and it is possible to provide the liquid level detecting apparatus in which the arm holder smoothly moves.
Besides, a rotation regulating portion for regulating a rotation range of the float arm is provided at at least one of the first and the second frames, and a weld fixing portion for welding the first and the second frames is provided near the rotation regulating portion. By the structure like this, it is possible to provide the liquid level detecting apparatus which can prevent the first and the second frames from coming out by the movement of the float arm in a direction other than the sliding direction caused by liquid level variation.
Besides, the weld fixing portion is a positioning member for determining a positional relation of the first and the second frames. By the structure like this, the positioning member and the weld fixing portion are formed at the same portion, so that the further small liquid level detecting apparatus can be provided.
Besides, a reinforcing rib is provided at a rear surface of the second frame. By the structure like this, the rigidity of the second frame is raised, and the small and strong liquid level detecting apparatus can be provided.